CN113508207B

CN113508207B - Excavator

Info

Publication number: CN113508207B
Application number: CN202080017783.8A
Authority: CN
Inventors: 佐野公则; 白谷龙二
Original assignee: Sumitomo SHI Construction Machinery Co Ltd
Current assignee: Sumitomo SHI Construction Machinery Co Ltd
Priority date: 2019-03-29
Filing date: 2020-03-27
Publication date: 2023-12-22
Anticipated expiration: 2040-03-27
Also published as: EP3951087B1; US12018460B2; EP3951087A1; JPWO2020203906A1; CN113508207A; KR20210143740A; EP3951087A4; WO2020203906A1; US20220002975A1

Abstract

The invention provides an excavator. The shovel (100) is provided with a lower traveling body (1), an upper revolving body (3) rotatably mounted on the lower traveling body (1), an engine (11) mounted on the upper revolving body (3), a main pump (14) driven by the engine (11), and a controller (30) for controlling the flow rate of hydraulic oil discharged from the main pump (14). The controller (30) delays the responsiveness of the main pump (14) when the load of the engine (11) increases until the actual torque of the engine (11) rises to a level corresponding to the load.

Description

Excavator

Technical Field

The present invention relates to an excavator as an excavator.

Background

Conventionally, there is known an excavator in which the discharge amount of a hydraulic pump is controlled so that the absorption torque of the hydraulic pump does not exceed the rated torque of an engine even when the discharge pressure of the hydraulic pump changes (refer to patent document 1).

When the engine load is small, the actual torque of the engine rotating at a prescribed rotational speed changes at a level smaller than the rated torque. Then, when the engine load increases, the actual torque increases by an increase in the fuel injection amount, and reaches the rated torque. In this way, the actual torque dynamically changes, and increases with a certain delay when the engine load increases.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2009-2318

Disclosure of Invention

Technical problem to be solved by the invention

However, the control in the above-described shovel does not take into account the delay associated with the rise of the actual torque of the engine. Therefore, in the control of the shovel, the absorption torque of the hydraulic pump temporarily exceeds the actual torque of the engine, and there is a possibility that the engine rotation speed may be lowered.

Therefore, it is desirable to more reliably prevent the absorption torque of the hydraulic pump from exceeding the actual torque of the engine.

Means for solving the technical problems

An excavator according to an embodiment of the present invention includes: a lower traveling body; an upper revolving body rotatably mounted on the lower traveling body; an engine mounted on the upper revolving unit; a hydraulic pump driven by the engine; and a control device that controls a flow rate of the hydraulic oil discharged from the hydraulic pump, wherein the control device delays responsiveness of the hydraulic pump until an actual torque of the engine increases to a level corresponding to the load when the load of the engine increases.

ADVANTAGEOUS EFFECTS OF INVENTION

With the above arrangement, it is possible to provide an excavator capable of more reliably preventing the absorption torque of the hydraulic pump from exceeding the actual torque of the engine.

Drawings

Fig. 1 is a side view of an excavator according to an embodiment of the present invention.

Fig. 2 is a diagram showing a configuration example of a hydraulic system mounted on an excavator.

Fig. 3 is a diagram showing a configuration example of the controller.

Fig. 4 shows an example of a change over time in the value related to the fluctuation suppression process when the boom raising operation is performed.

Fig. 5 shows another example of the time-dependent change of the value in the fluctuation suppression process when the boom raising operation is performed.

Detailed Description

First, an excavator 100 as an excavator according to an embodiment of the present invention will be described with reference to fig. 1. Fig. 1 is a side view of an excavator 100. In the present embodiment, an upper revolving unit 3 is rotatably mounted on a lower traveling body 1 via a revolving mechanism 2. The lower traveling body 1 is driven by a hydraulic motor 2M for traveling. The hydraulic motor 2M for traveling includes a hydraulic motor 2ML for left traveling that drives a left crawler belt and a hydraulic motor 2MR for right traveling that drives a right crawler belt (not visible in fig. 1). The turning mechanism 2 is driven by a turning hydraulic motor 2A mounted on the upper turning body 3. However, the hydraulic motor 2A for turning may be a motor generator for turning as an electric actuator.

A boom 4 is attached to the upper revolving unit 3. An arm 5 is attached to the tip end of the boom 4, and a bucket 6 as a termination attachment is attached to the tip end of the arm 5. The boom 4, the arm 5, and the bucket 6 constitute an excavating attachment as an example of an attachment. The boom 4 is driven by a boom cylinder 7, the arm 5 is driven by an arm cylinder 8, and the bucket 6 is driven by a bucket cylinder 9.

The upper revolving structure 3 is provided with a cockpit 10 serving as a cab, and is equipped with a power source such as an engine 11. A controller 30 is attached to the upper revolving unit 3. In the present specification, for convenience, the side of the upper revolving structure 3 to which the boom 4 is attached is referred to as the front side, and the side to which the counterweight (counter weight) is attached is referred to as the rear side.

The controller 30 is a control device for controlling the shovel 100. In the present embodiment, the controller 30 is configured by a computer including a CPU, a volatile memory device, a nonvolatile memory device, and the like. The controller 30 is configured to read out programs corresponding to various functional elements from a nonvolatile memory device, load the programs into a volatile memory device such as a RAM, and execute corresponding processes by a CPU, thereby realizing various functions.

Next, a configuration example of a hydraulic system mounted on the shovel 100 will be described with reference to fig. 2. Fig. 2 shows an example of the configuration of a hydraulic system mounted on the shovel 100. In fig. 2, the mechanical power transmission system, the hydraulic oil line, the pilot line, and the electrical control system are shown by double lines, solid lines, broken lines, and dotted lines, respectively.

The hydraulic system of the shovel 100 mainly includes an engine 11, a regulator 13, a main pump 14, a pilot pump 15, a control valve 17, an operation device 26, a discharge pressure sensor 28, an operation pressure sensor 29, a controller 30, an engine rotation speed adjustment dial 75, and the like.

In fig. 2, the hydraulic system circulates hydraulic oil from the main pump 14 driven by the engine 11 to the hydraulic oil tank through at least one of the intermediate bypass line 40 and the parallel line 42.

The engine 11 is a driving source of the shovel 100. In the present embodiment, the engine 11 is, for example, a diesel engine that operates so as to maintain a predetermined rotational speed. The output shaft of the engine 11 is coupled to the input shafts of the main pump 14 and the pilot pump 15, respectively. The engine 11 is provided with a supercharger. In the present embodiment, the supercharger is a turbocharger. The engine 11 is controlled by an engine control unit. The engine control unit is configured to adjust the fuel injection amount according to a boost pressure (boost pressure), for example. The boost pressure is detected, for example, by a boost pressure sensor.

The main pump 14 is configured to supply hydraulic oil to the control valve 17 via a hydraulic oil line. In the present embodiment, the main pump 14 is an electrically controlled hydraulic pump. Specifically, the main pump 14 is a swash plate type variable capacity hydraulic pump.

The regulator 13 controls the discharge amount of the main pump 14. In the present embodiment, the regulator 13 controls the discharge amount of the main pump 14 by controlling the displacement of the main pump 14 per one rotation by adjusting the swash plate tilting angle of the main pump 14 in accordance with a control command from the controller 30.

The pilot pump 15 is configured to supply hydraulic oil to a hydraulic control device including an operation device 26 via a pilot line. In the present embodiment, the pilot pump 15 is a fixed displacement hydraulic pump. The pilot pump 15 may be omitted. At this time, the function assumed by the pilot pump 15 may be realized by the main pump 14. That is, the main pump 14 may have a function of supplying the hydraulic oil to the operation device 26 or the like after the pressure of the hydraulic oil is reduced by the throttle or the like, in addition to the function of supplying the hydraulic oil to the control valve 17.

The control valve 17 is a hydraulic control device that controls a hydraulic system in the shovel 100. In the present embodiment, as shown by a one-dot chain line, the control valve 17 includes control valves 171 to 176. The control valve 175 includes a control valve 175L and a control valve 175R, and the control valve 176 includes a control valve 176L and a control valve 176R. The control valve 17 is capable of selectively supplying the hydraulic oil discharged from the main pump 14 to one or more hydraulic actuators through the control valves 171 to 176. The control valves 171 to 176 control the flow rate of the hydraulic oil flowing from the main pump 14 to the hydraulic actuator and the flow rate of the hydraulic oil flowing from the hydraulic actuator to the hydraulic oil tank. The hydraulic actuators include a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, a left travel hydraulic motor 2ML, a right travel hydraulic motor 2MR, and a swing hydraulic motor 2A.

The operating device 26 is a device for an operator to operate the actuator. The actuator includes at least one of a hydraulic actuator and an electric actuator. In the present embodiment, the operation device 26 supplies the hydraulic oil discharged from the pilot pump 15 to the pilot port of the corresponding control valve in the control valve 17 via the pilot line. The pilot pressure, which is the pressure of the hydraulic oil supplied to each pilot port, is a pressure corresponding to the operation direction and the operation amount of a lever or pedal (not shown) of the operation device 26, and the lever or pedal of the operation device 26 corresponds to the hydraulic actuator.

The discharge pressure sensor 28 is configured to detect the discharge pressure of the main pump 14. In the present embodiment, the discharge pressure sensor 28 outputs the detected value to the controller 30.

The operation pressure sensor 29 is configured to detect the content of the operation via the operation device 26. In the present embodiment, the operation pressure sensor 29 detects the operation direction and the operation amount of the lever or the pedal as the operation device 26 corresponding to the actuator, respectively, as a pressure (operation pressure), and outputs the detected values to the controller 30. The operation content of the operation device 26 may be detected by a sensor other than the operation pressure sensor.

The main pump 14 includes a left main pump 14L and a right main pump 14R. The left main pump 14L circulates hydraulic oil to the hydraulic oil tank through the left intermediate bypass line 40L or the left parallel line 42L, and the right main pump 14R circulates hydraulic oil to the hydraulic oil tank through the right intermediate bypass line 40R or the right parallel line 42R.

The left intermediate bypass line 40L is a hydraulic line passing through control valves 171, 173, 175L, and 176L disposed in the control valve 17. The right intermediate bypass line 40R is a hydraulic line passing through control valves 172, 174, 175R, and 176R disposed in the control valve 17.

The control valve 171 is a spool valve for switching the flow of hydraulic oil so as to supply hydraulic oil discharged from the left main pump 14L to the left traveling hydraulic motor 2ML and discharge hydraulic oil discharged from the left traveling hydraulic motor 2ML to the hydraulic oil tank.

The control valve 172 is a spool valve for switching the flow of hydraulic oil so as to supply hydraulic oil discharged from the right main pump 14R to the right traveling hydraulic motor 2MR and discharge hydraulic oil discharged from the right traveling hydraulic motor 2MR to the hydraulic oil tank.

The control valve 173 is a spool valve for switching the flow of hydraulic oil so as to supply hydraulic oil discharged from the left main pump 14L to the turning hydraulic motor 2A and discharge hydraulic oil discharged from the turning hydraulic motor 2A to the hydraulic oil tank.

The control valve 174 is a spool valve for switching the flow of hydraulic oil so as to supply hydraulic oil discharged from the right main pump 14R to the bucket cylinder 9 and discharge hydraulic oil in the bucket cylinder 9 to the hydraulic oil tank.

The control valve 175L is a spool valve that switches the flow of hydraulic oil so as to supply hydraulic oil discharged from the left main pump 14L to the boom cylinder 7. The control valve 175R is a spool valve for switching the flow of hydraulic oil so as to supply hydraulic oil discharged from the right main pump 14R to the boom cylinder 7 and discharge hydraulic oil in the boom cylinder 7 to the hydraulic oil tank.

The control valve 176L is a spool valve for switching the flow of hydraulic oil so as to supply hydraulic oil discharged from the left main pump 14L to the arm cylinder 8 and discharge hydraulic oil in the arm cylinder 8 to the hydraulic oil tank. The control valve 176R is a spool valve for switching the flow of hydraulic oil so as to supply hydraulic oil discharged from the right main pump 14R to the arm cylinder 8 and discharge hydraulic oil in the arm cylinder 8 to the hydraulic oil tank.

The left parallel line 42L is a hydraulic line parallel to the left intermediate bypass line 40L. When the flow of the working oil through the left intermediate bypass line 40L is restricted or shut off by any one of the control valves 171, 173, and 175L, the left parallel line 42L can supply the working oil to the control valve further downstream. The right parallel line 42R is a working oil line in parallel with the right intermediate bypass line 40R. When the flow of the working oil through the right intermediate bypass line 40R is restricted or shut off by any one of the control valves 172, 174, and 175R, the right parallel line 42R can supply the working oil to the control valve further downstream.

The regulator 13 includes a left regulator 13L and a right regulator 13R. The left regulator 13L is configured to be capable of controlling the discharge amount of the left main pump 14L by regulating the swash plate tilting angle of the left main pump 14L according to the discharge pressure of the left main pump 14L. This control is called power control or horsepower control. Specifically, the left regulator 13L regulates the swash plate tilting angle of the left main pump 14L in response to an increase in the discharge pressure of the left main pump 14L, for example, to reduce the discharge amount by reducing the displacement per one rotation. The same applies to the right adjuster 13R. This is to avoid that the suction power (e.g., suction horsepower) of the main pump 14, which is represented by the product of the discharge pressure and the discharge amount, exceeds the output power (e.g., output horsepower) of the engine 11.

The operating device 26 includes a left operating lever 26L, a right operating lever 26R, and a travel lever 26D. The walking bar 26D includes a left walking bar 26DL and a right walking bar 26DR.

The left lever 26L is used for swing operation and operation of the arm 5. When the left operation lever 26L is operated in the forward and backward direction, the pilot pressure corresponding to the lever operation amount is introduced to the pilot port of the control valve 176 by the hydraulic oil discharged from the pilot pump 15. When the operation is performed in the left-right direction, the pilot pressure corresponding to the lever operation amount is introduced to the pilot port of the control valve 173 by the hydraulic oil discharged from the pilot pump 15.

Specifically, when the operation is performed in the arm closing direction, the left operation lever 26L causes hydraulic oil to be introduced into the right pilot port of the control valve 176L, and causes hydraulic oil to be introduced into the left pilot port of the control valve 176R. When the arm is operated in the opening direction, the left operation lever 26L causes hydraulic oil to be introduced into the left pilot port of the control valve 176L and hydraulic oil to be introduced into the right pilot port of the control valve 176R. The left lever 26L causes hydraulic oil to be introduced into the left pilot port of the control valve 173 when the left turning direction is operated, and causes hydraulic oil to be introduced into the right pilot port of the control valve 173 when the right turning direction is operated.

The right operation lever 26R is used for the operation of the boom 4 and the operation of the bucket 6. When the lever is operated in the forward and backward direction, the right operation lever 26R causes the pilot pressure corresponding to the lever operation amount to be introduced into the pilot port of the control valve 175 by the hydraulic oil discharged from the pilot pump 15. When the operation is performed in the left-right direction, the pilot pressure corresponding to the lever operation amount is introduced to the pilot port of the control valve 174 by the hydraulic oil discharged from the pilot pump 15.

Specifically, when the boom lowering direction is operated, the right operation lever 26R introduces hydraulic oil to the right pilot port of the control valve 175R. When the boom raising direction is operated, the right control lever 26R causes hydraulic oil to be introduced into the right pilot port of the control valve 175L and hydraulic oil to be introduced into the left pilot port of the control valve 175R. When the operation is performed in the bucket closing direction, the right operation lever 26R causes hydraulic oil to be introduced into the left pilot port of the control valve 174, and when the operation is performed in the bucket opening direction, hydraulic oil is introduced into the right pilot port of the control valve 174.

The walking bar 26D is used for the operation of the crawler. Specifically, the left walking bar 26DL is used for the operation of the left crawler. The left travel bar 26DL may be configured to be interlocked with the left travel pedal. When the left traveling lever 26DL is operated in the forward and backward direction, the pilot pressure corresponding to the lever operation amount is introduced to the pilot port of the control valve 171 by the hydraulic oil discharged from the pilot pump 15. Right walking bar 26DR is used for right track operation. The right travel bar 26DR is configured to be interlocked with a right travel pedal. When the lever is operated in the forward and backward direction, the right traveling lever 26DR causes the pilot pressure corresponding to the lever operation amount to be introduced to the pilot port of the control valve 172 by the hydraulic oil discharged from the pilot pump 15.

The discharge pressure sensor 28 includes a discharge pressure sensor 28L and a discharge pressure sensor 28R. The discharge pressure sensor 28L detects the discharge pressure of the left main pump 14L, and outputs the detected value to the controller 30. The same applies to the discharge pressure sensor 28R.

The operation pressure sensors 29 include operation pressure sensors 29LA, 29LB, 29RA, 29RB, 29DL, and 29DR. The operation pressure sensor 29LA detects the operation content in the front-rear direction of the left operation lever 26L as pressure, and outputs the detected value to the controller 30. The operation content is, for example, a lever operation direction, a lever operation amount (lever operation angle), and the like.

Similarly, the operation pressure sensor 29LB detects the operation content in the left-right direction of the left operation lever 26L as pressure, and outputs the detected value to the controller 30. The operation pressure sensor 29RA detects the operation content in the forward and backward direction of the right operation lever 26R as pressure, and outputs the detected value to the controller 30. The operation pressure sensor 29RB detects the operation content in the right-left direction of the right operation lever 26R as pressure, and outputs the detected value to the controller 30. The operation pressure sensor 29DL detects the operation content in the forward and backward direction of the left travel bar 26DL as pressure, and outputs the detected value to the controller 30. The operation pressure sensor 29DR detects the operation content in the forward-backward direction of the right walking lever 26DR as pressure, and outputs the detected value to the controller 30.

The controller 30 may receive the output of the operation pressure sensor 29 and output a control instruction to the regulator 13 as needed to change the discharge amount of the main pump 14.

The controller 30 is configured to execute negative control as energy saving control using the throttle 18 and the control pressure sensor 19. The throttle 18 includes a left throttle 18L and a right throttle 18R, and the control pressure sensor 19 includes a left control pressure sensor 19L and a right control pressure sensor 19R. In the present embodiment, the control pressure sensor 19 functions as a negative control pressure sensor. The energy saving control is control for reducing the discharge amount of the main pump 14 in order to suppress wasteful energy consumption by the main pump 14.

A left throttle 18L is disposed in the left intermediate bypass line 40L between the control valve 176L located furthest downstream and the hydraulic oil tank. Therefore, the flow of hydraulic oil discharged from the left main pump 14L is restricted by the left throttle 18L. Also, the left throttle 18L generates a control pressure (negative control pressure) for controlling the left regulator 13L. The left control pressure sensor 19L is a sensor for detecting the control pressure, and outputs the detected value to the controller 30. The controller 30 adjusts the swash plate tilting angle of the left main pump 14L based on the control pressure, and controls the discharge amount of the left main pump 14L by negative control. The controller 30 decreases the discharge amount of the left main pump 14L as the control pressure increases, and increases the discharge amount of the left main pump 14L as the control pressure decreases. The discharge amount of the right main pump 14R is controlled in the same manner.

Specifically, as shown in fig. 2, when none of the hydraulic actuators in the shovel 100 is operated, that is, when the shovel 100 is in the standby state, the hydraulic oil discharged from the left main pump 14L reaches the left throttle 18L through the left intermediate bypass line 40L. The flow of hydraulic oil discharged from the left main pump 14L increases the control pressure generated upstream of the left throttle 18L. As a result, the controller 30 reduces the discharge amount of the left main pump 14L to the standby (standby) flow rate, and suppresses the pressure loss (pump loss) when the discharged hydraulic oil passes through the left intermediate bypass line 40L. The standby flow rate is a predetermined flow rate used in the standby state, for example, a minimum allowable discharge amount. On the other hand, when any one of the hydraulic actuators is operated, the hydraulic oil discharged from the left main pump 14L flows into the hydraulic actuator to be operated via the control valve corresponding to the hydraulic actuator to be operated. Then, the control valve corresponding to the hydraulic actuator to be operated reduces or eliminates the flow rate of the hydraulic oil reaching the left restrictor 18L, thereby reducing the control pressure generated upstream of the left restrictor 18L. As a result, the controller 30 increases the discharge amount of the left main pump 14L, and circulates enough hydraulic oil to the hydraulic actuator to be operated, so that the hydraulic actuator to be operated is reliably driven. In addition, the controller 30 similarly controls the discharge amount of the right main pump 14R.

By the negative control as described above, the hydraulic system of fig. 2 can suppress wasteful energy consumption in the main pump 14 in the standby state. The wasted energy consumption includes pump losses in the intermediate bypass line 40 caused by hydraulic oil discharged from the main pump 14. Further, when the hydraulic actuator is operated, the hydraulic system of fig. 2 can reliably supply the sufficient required hydraulic oil from the main pump 14 to the hydraulic actuator of the work object.

The engine rotation speed adjustment dial 75 is a dial for adjusting the rotation speed of the engine 11. The engine speed adjustment dial 75 transmits data indicating the set state of the engine speed to the controller 30. In the present embodiment, the engine speed adjustment dial 75 is configured to be capable of switching the engine speed in 4 stages of SP mode, H mode, a mode, and IDLE mode. The SP mode is a rotation speed mode selected when priority is given to the workload, and the highest engine rotation speed is used. The H mode is a rotation speed mode selected when the workload and the fuel consumption rate are to be combined, and the second highest engine rotation speed is used. The a-mode is a rotation speed mode selected when the shovel 100 is operated with low noise while giving priority to the fuel consumption rate, and uses the engine rotation speed of the third highest. The IDLE mode is a rotation speed mode selected when the engine 11 is set to an IDLE operation state, and the lowest engine rotation speed is used. The engine 11 is constantly controlled in the engine speed in the rotation speed mode set by the engine speed adjustment dial 75.

Next, a process (hereinafter, referred to as "fluctuation suppression process") in which the controller 30 suppresses fluctuation of the flow rate command value Q output to the regulator 13 will be described with reference to fig. 3. Fig. 3 is a diagram showing a configuration example of the controller 30.

In the present embodiment, the controller 30 includes a requested torque calculation unit E1, a torque restriction unit E2, a fluctuation suppression unit E3, and a flow rate command calculation unit E4. The controller 30 is configured to receive the required flow rate Q for each predetermined control period ^* Discharge pressure P and boost pressure P _B Etc. as input, and outputs a torque limit value T' _limit Flow rate command value Q, and the like.

Required flow rate Q ^* Is a value calculated as the flow rate of hydraulic oil to be discharged from the main pump 14. The controller 30 calculates the required flow rate Q based on at least one of the control pressure detected by the control pressure sensor 19, the discharge pressure detected by the discharge pressure sensor 28, the operation pressure detected by the operation pressure sensor 29, and the like, for example ^* . Required flow rate Q ^* Or may be calculated by the control pressure sensor 19. At this time, the control pressure sensor 19 outputs the required flow rate Q to the controller 30 ^* . In the present embodiment, the controller 30 calculates the required flow rate Q from the control pressure detected by the control pressure sensor 19 ^* 。

The required torque calculation unit E1 is configured to calculate a required torque T ^* . Required torque T ^* Is to achieve the required flow rate Q ^* A value calculated from the torque required. In the present embodiment, the required torque calculating unit E1 receives the required flow rate Q ^* And discharge pressure P as input, and calculating a required torque T using (1) ^* 。

[ number 1]

The torque limiter E2 is configured to limit the required torque T ^* . In the present embodiment, the torque limiter E2 limits the required torque T ^* So that the required torque T ^* And not exceeding the rated torque of the engine 11. Specifically, the torque limiter E2 receives the required torque T calculated by the required torque calculator E1 ^* And the boost pressure P detected by the boost pressure sensor _B As an input, and outputs the allowable torque T to the fluctuation suppression section E3 _limit . More specifically, the torque limiter E2 is based on the boost pressure P _B Calculating the allowable torque T corresponding to the uniquely determined load rate L _limit . The load factor L (%) is, for example, the allowable torque T of the engine 11 _limit Ratio relative to the rated torque of the engine. Equation (2) represents allowable torque T _limit Required torque T ^* And the load factor L (%).

[ number 2]

T _limit ＝T ^* ×L ……(2)

The fluctuation suppression unit E3 is configured to suppress the allowable torque T _limit Is a variation of (a). In the present embodiment, the fluctuation suppression section E3 serves as the time constant T _S Is configured to limit the allowable torque T for each predetermined control period _limit Is a variable range of (a). Specifically, the fluctuation suppression unit E3 receives the allowable torque T calculated by the torque restriction unit E2 _1imit As an input, and outputs a torque limit value T' to the flow rate instruction calculating section E4 " _limit 。

The flow rate command calculation unit E4 is configured to calculate a flow rate command value Q output to the regulator 13. In the present embodiment, the flow rate command is calculatedThe unit E4 receives the discharge pressure P detected by the discharge pressure sensor 28 and the torque limit value T "calculated by the fluctuation suppression unit E3" _limit As an input, a flow rate command value Q is calculated using equation (3).

[ number 3]

In this way, the controller 30 obtains the requested flow rate Q by the torque limiter E2 and the fluctuation suppressor E3 ^* And the output state of the engine 11 at the discharge pressure P (torque limit value T': _1imit ) And calculates a flow rate command value Q corresponding to the output state of the engine 11 by the flow rate command calculation unit E4. With the above structure, the controller 30 can prevent the pressure P from being increased _B The flow rate command value Q excessively increases before the rise is sufficiently completed. Therefore, the controller 30 can prevent the absorption torque of the main pump 14 from excessively increasing in a state where the actual torque of the engine 11 is low. That is, the controller 30 can prevent the engine rotational speed from suddenly decreasing due to a sudden increase in the absorption torque of the main pump 14 when the actual torque of the engine 11 is low. This is because, even when the absorption torque of the main pump 14 is lower than the rated torque of the engine 11, if the absorption torque of the main pump 14 exceeds the actual torque of the engine 11, the engine speed is reduced. In addition, the absorption torque of the main pump 14 is typically represented by the product of the discharge pressure and the discharge amount. In this way, the controller 30 can more reliably prevent the torque at the boost pressure P by preventing the absorption torque of the main pump 14 from exceeding the actual torque of the engine 11 _B The engine speed decreases before the full increase.

Next, the effect of the fluctuation suppression process will be described with reference to fig. 4. Fig. 4 shows a change with time of a value related to the fluctuation suppression process when the boom raising operation is performed. Specifically, fig. 4 includes fig. 4 (a) and fig. 4 (B). Fig. 4 (a) shows a change with time of a value related to torque. The torque-related value includes the allowable torque T _limit Torque limit value T' _limit . Fig. 4 (B) shows the change in engine speed with time.

More specifically, FIG. 4(A) The broken line of (a) represents the allowable torque T that the torque limiter E2 derives for each predetermined control cycle _limit Time-dependent changes. The solid line in fig. 4 (a) shows the torque limit value T "that the fluctuation suppression section E3 derives for each predetermined control period" _limit Time-dependent changes. The broken line in fig. 4 (B) shows that when the fluctuation suppression section E3 is not present, that is, the torque limit value T "is replaced" _limit While allowing torque T _limit The engine rotational speed when input to the flow rate command calculation unit E4 changes with time. The solid line in fig. 4 (B) shows the torque limit value T "when the fluctuation suppression section E3 is present" _limit The engine rotational speed when input to the flow rate command calculation unit E4 changes with time.

From time t0 to time t1, the hydraulic load due to the operation is not applied to the engine 11. During this period, the controller 30 also estimates that the requested flow rate Q is based on the torque limiter E2 and the fluctuation limiter E3 ^* And the output state of the engine 11 at the discharge pressure P (torque limit value T': _limit ) And calculates a flow rate command value Q corresponding to the output state of the engine 11 by the flow rate command calculation unit E4. Therefore, the controller 30 also calculates the torque limit value t″ that delays the responsiveness of the main pump 14 before the load of the engine 11 increases " _limit . Therefore, the controller 30 calculates a flow rate command value Q that delays the responsiveness of the main pump 14.

Therefore, the controller 30 can reduce the engine output by calculating the smaller flow instruction value Q in a state where a larger load is not applied.

At time t1, when the right control lever 26R is operated in the boom raising direction, the control valve 175 moves to shut off the intermediate bypass line 40, and the control pressure detected by the control pressure sensor 19 decreases. Therefore, the required flow rate Q calculated from the control pressure ^* As the control pressure decreases, it increases. On the other hand, the discharge pressure P detected by the discharge pressure sensor 28 is associated with the required flow rate Q ^* And the actual discharge amount increases due to the increase in (a). Thus, according to the required flow rate Q ^* And a requested torque T calculated from the discharge pressure P ^* Rapid increase according to the required torque T ^* Calculated allowable torque T _limit Also as in (A) of FIG. 4As shown by the dashed line.

When the fluctuation suppression section E3 is not present, that is, when the torque limit value T "is replaced" _limit While allowing torque T _limit When input to the flow rate command calculation unit E4, the engine speed decreases as indicated by the broken line in fig. 4 (B). This is because the absorption torque of the main pump 14 temporarily exceeds the actual torque of the engine 11. This is because, compared with the case where the fluctuation suppression section E3 is present, that is, compared with the torque limit value t″ " _limit The actual discharge amount of the main pump 14, which is the flow rate command value Q, becomes larger than that of the case where the flow rate command value Q is input to the flow rate command calculation unit E4. This rapid increase in the actual discharge amount of the main pump 14 is at the required flow rate Q ^* The same may occur when the flow rate command value Q is directly used.

Therefore, in the example of fig. 4, the controller 30 (flow rate command calculation unit E4) calculates the torque limit value t″ from the fluctuation suppression unit E3 " _limit To determine the flow rate command value Q, thereby suppressing a sudden increase in the actual discharge amount of the main pump 14. As a result, the controller 30 can maintain the engine speed as indicated by the solid line in fig. 4 (B), and can prevent the engine speed from greatly decreasing as indicated by the broken line in fig. 4 (B). This is because the controller 30 can prevent the absorption torque of the main pump 14 from exceeding the actual torque of the engine 11.

Next, the effect of the fluctuation suppressing process by the controller 30 including the other fluctuation suppressing section E3 will be described with reference to fig. 5. Fig. 5 shows a change with time in the value of the fluctuation suppression process when the boom raising operation is performed, similarly to fig. 4. Specifically, fig. 5 includes fig. 5 (a) and fig. 5 (B). Fig. 5 (a) shows a change with time in a value related to torque. The torque-related value includes the allowable torque T _limit Torque limit value T' _limit . Fig. 5 (B) shows the change in engine speed with time.

In the example of fig. 5, the fluctuation suppression section E3 is configured to respond to the target rotation speed ω of the engine 11 ^* Determining a torque limit value T' from a difference Deltaomega from an actual rotational speed omega " _limit 。

Target rotation speed ω of engine 11 ^* For example, in order to give a process to the engine 11 that does not become overloadedThe additional load is higher than the current engine speed by a speed difference corresponding to the additional load.

Specifically, the fluctuation suppression unit E3 receives the allowable torque T calculated by the torque restriction unit E2 _limit Target rotational speed ω ^* And an actual rotation speed ω detected by an engine rotation speed sensor (not shown) as an input, and a torque limit value t″ is calculated using (4) " _limit . In addition, coefficient K _P Is a proportionality constant, coefficient K _I Is an integral constant.

[ number 4]

T″ _limit ＝(ω ^* -ω)×K _P +∫(ω ^* -ω)dt×K _I

＝Δω×K _P +∫Δωdt×K _I ……(4)

More specifically, the broken line of fig. 5 (a) represents the allowable torque T _limit The solid line of (A) of FIG. 5 represents the torque limit value T' calculated using equation (4) over time " _limit Time-dependent changes. Further, the broken line of fig. 5 (B) indicates that the fluctuation suppression section E3 is not present, that is, the torque limit value T "is replaced" _limit While allowing torque T _limit The engine rotational speed when input to the flow rate command calculation unit E4 changes with time. The solid line in fig. 5 (B) shows the torque limit value T "calculated by using the equation (4) when the fluctuation suppression section E3 is present" _limit The engine rotational speed when input to the flow rate command calculation unit E4 changes with time.

At time t1, when the right control lever 26R is operated in the boom raising direction, the control valve 175 moves to shut off the intermediate bypass line 40, and the control pressure detected by the control pressure sensor 19 decreases. Therefore, the required flow rate Q calculated from the control pressure ^* As the control pressure decreases, it increases. On the other hand, the discharge pressure P detected by the discharge pressure sensor 28 is associated with the required flow rate Q ^* And the actual discharge amount increases due to the increase in (a). Thus, according to the required flow rate Q ^* And a requested torque T calculated from the discharge pressure P ^* Rapid increase according to the required torque T ^* Calculated allowable torque T _limit As also indicated by the broken line of FIG. 5 (A)Which is shown to be increasing.

When the fluctuation suppression section E3 is not present, that is, when the torque limit value T "is replaced" _limit While allowing torque T _limit When input to the flow rate command calculation unit E4, the engine speed decreases as indicated by the broken line in fig. 5 (B). This is because the absorption torque of the main pump 14 temporarily exceeds the actual torque of the engine 11. This is because, compared with the case where the fluctuation suppression section E3 is present, that is, compared with the torque limit value T "calculated using the expression (4)" _limit The actual discharge amount of the main pump 14, which is the flow rate command value Q, becomes larger than that of the case where the flow rate command value Q is input to the flow rate command calculation unit E4. This rapid increase in the actual discharge amount of the main pump 14 is at the required flow rate Q ^* The same may occur when the flow rate command value Q is directly used.

Therefore, in the example of fig. 5, as in the case of the example of fig. 4, the controller 30 calculates the torque limit value t″ by using the expression (4) " _limit To determine the flow rate command value Q, thereby suppressing a sudden increase in the actual discharge amount of the main pump 14. As a result, the controller 30 can maintain the engine speed as indicated by the solid line in fig. 5 (B), and can prevent the engine speed from greatly decreasing as indicated by the broken line in fig. 5 (B). This is because the controller 30 can prevent the absorption torque of the main pump 14 from exceeding the actual torque of the engine 11. Specifically, this is because the controller 30 uses, as the target rotational speed ω, a value higher than the current engine rotational speed by a rotational speed difference corresponding to an additional load to such an extent that the engine rotational speed does not become an overload, for the engine 11 ^* This allows the absorption torque of the main pump 14 to be gradually increased (not abruptly increased).

As described above, the shovel 100 includes the lower traveling body 1, the upper revolving structure 3 rotatably mounted on the lower traveling body 1, the engine 11 mounted on the upper revolving structure 3, the main pump 14 as a hydraulic pump driven by the engine 11, and the controller 30 as a control device for controlling the flow rate of the hydraulic oil discharged from the main pump 14. When the load of the engine 11 increases, the controller 30 is configured to delay (decrease) the responsiveness of the main pump 14 until the actual torque of the engine 11 increases to a level corresponding to the load.

With this structure, the shovel 100 can more reliably prevent the absorption torque of the main pump 14 from exceeding the actual torque of the engine 11. In other words, the shovel 100 can effectively increase the absorption torque of the main pump 14, that is, the actual torque of the engine 11. This is because the shovel 100 can predict a delay in the rise of the engine output and limit the discharge amount of the main pump 14 in advance. That is, this is because the shovel 100 can cope with dynamic changes in the actual torque of the engine 11. Therefore, the shovel 100 can suppress a decrease in the engine rotation speed. As a result, the shovel 100 can improve the fuel consumption rate. Further, the shovel 100 can reduce the uncomfortable feeling felt by the operator with respect to the rotational speed variation of the engine during operation.

Further, by providing the fluctuation suppression section E3, the shovel 100 can prevent the engine load, which is the absorption torque of the main pump 14, from increasing sharply and prevent the engine rotation speed from becoming unstable, not only when the boost pressure is relatively low but also when the boost pressure is relatively high.

The controller 30 may be configured to increase the flow rate of the hydraulic oil discharged from the main pump 14 in accordance with an increase in the actual torque of the engine 11 by a method other than the method in the above-described embodiment. For example, the controller 30 may be configured to increase the flow rate of the hydraulic oil discharged from the main pump 14 at an increase rate corresponding to an increase in the actual torque of the engine 11. At this time, the rate of increase in the flow rate of the hydraulic oil discharged from the main pump 14 may be set in advance based on at least one of past data, simulation results, and the like.

The controller 30 may be configured to use a method other than the method in the above embodiment to request the flow rate Q, which is the flow rate of the hydraulic oil to be discharged from the main pump 14 ^* Is suppressed, and an increase in the flow rate command value Q corresponding to the flow rate of the hydraulic oil actually discharged from the main pump 14 is suppressed.

The controller 30 may be configured to realize the required flow rate Q by a method other than the method in the above embodiment ^* Required torque T ^* To calculate the torque limit value T' _limit And according to the torque limit value T' _limit To calculate the flow rate command value Q.

The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiment. The above-described embodiments can be applied to various modifications, substitutions, and the like without departing from the scope of the present invention. The features described above can be combined without causing any technical contradiction.

For example, in the above-described embodiment, the hydraulic system mounted on the shovel 100 is configured to be capable of executing negative control as energy saving control, but may be configured to be capable of executing positive control, load sensing control, or the like. When positive control is employed, the controller 30 may be configured to calculate the required flow rate Q based on the operation pressure detected by the operation pressure sensor 29, for example ^* . When the load sensing control is adopted, the controller 30 may be configured to calculate the required flow rate Q based on, for example, the output of a load pressure sensor that detects the pressure of the hydraulic oil in the actuator and the discharge pressure detected by the discharge pressure sensor 28 ^* 。

In the above embodiment, the controller 30 executes the fluctuation suppression process when the boom raising operation is performed, but may execute the fluctuation suppression process when at least one of the boom lowering operation, the arm closing operation, the arm opening operation, the bucket closing operation, the bucket opening operation, the swing operation, the travel operation, and the like is performed.

In the above embodiment, a hydraulic lever including a hydraulic pilot circuit is disclosed. For example, in the hydraulic pilot circuit related to the left operation lever 26L, the hydraulic oil supplied from the pilot pump 15 to the left operation lever 26L is transmitted to the pilot port of the control valve 176 at a flow rate corresponding to the opening degree of the remote control valve that opens and closes by the tilting of the left operation lever 26L in the arm opening direction. Alternatively, in the hydraulic pilot circuit related to the right operation lever 26R, the hydraulic oil supplied from the pilot pump 15 to the right operation lever 26R is transmitted to the pilot port of the control valve 175 at a flow rate corresponding to the opening degree of the remote control valve that opens and closes by the tilting of the right operation lever 26R in the boom raising direction.

However, not only a hydraulic lever including such a hydraulic pilot circuit but also an electric lever including an electric pilot circuit may be used. At this time, the lever operation amount of the electric lever is input to the controller 30 as an electric signal, for example. Further, an electromagnetic valve is disposed between the pilot pump 15 and the pilot port of each control valve. The solenoid valve is configured to operate in response to an electrical signal from the controller 30. With this configuration, when the manual operation using the electric lever is performed, the controller 30 can control the solenoid valve to increase or decrease the pilot pressure based on the electric signal corresponding to the lever operation amount, and can move the control valves.

The present application claims priority based on japanese patent application No. 2019-068992, filed on 3 months 29 in 2019, the entire contents of which are incorporated herein by reference.

Description of symbols

1-lower traveling body, 2-swing mechanism, 2-swing hydraulic motor, 2-M-traveling hydraulic motor, 2-ML-left traveling hydraulic motor, 2-MR-right traveling hydraulic motor, 3-upper swing body, 4-boom, 5-arm, 6-bucket, 7-boom cylinder, 8-arm cylinder, 9-bucket cylinder, 10-cockpit, 11-engine, 13-regulator, 14-main pump, 15-pilot pump, 17-control valve, 18-restrictor, 19-control pressure sensor, 26-operating device, 28-discharge pressure sensor, 29-operating pressure sensor, 30-controller, 40-intermediate bypass line, 42-parallel line, 75-engine rotation speed adjusting dial, 100-shovel, 171-176-control valve, E1-required torque calculation section, E2-torque restriction section, E3-variation inhibition section, E4-flow instruction calculation section.

Claims

1. An excavator, comprising:

a lower traveling body;

an upper revolving body rotatably mounted on the lower traveling body;

an engine mounted on the upper revolving unit;

a hydraulic pump driven by the engine; and

A control device for controlling the flow rate of the hydraulic oil discharged from the hydraulic pump,

the control device delays responsiveness of the hydraulic pump until an actual torque of the engine rises to a level corresponding to a load of the engine when the load of the engine increases,

the control device suppresses an increase in the flow rate of the hydraulic oil actually discharged by the hydraulic pump, with respect to an increase in the required flow rate, which is the flow rate of the hydraulic oil to be discharged by the hydraulic pump.

2. The excavator of claim 1, wherein,

the control device increases the flow rate of the hydraulic oil discharged from the hydraulic pump in response to an increase in the actual torque of the engine.

3. An excavator, comprising:

a lower traveling body;

an upper revolving body rotatably mounted on the lower traveling body;

an engine mounted on the upper revolving unit;

a hydraulic pump driven by the engine; and

the control device calculates a torque limit value from a required torque required to achieve a required flow rate, which is a flow rate of the hydraulic oil to be discharged by the hydraulic pump, and calculates a flow rate command value from the torque limit value.

4. The excavator of claim 3, wherein,

the control device also calculates a flow rate command value that delays responsiveness of the hydraulic pump before a load of the engine increases.

5. The excavator of claim 3, wherein,

the control device also calculates a torque limit value that delays responsiveness of the hydraulic pump before a load of the engine increases.